The Human Age: The World Shaped by Us

by Diane Ackerman

  In Bryan’s pale-blue office, I’d seen an old book on his desk, opened to favorite pages of colorful plates. Some of the shells were straw yellow and girdled by two or three narrow reddish-chestnut bands, others light-brown-capped with darker whorls, or cream and purple. Despite their different patterns and hues, they were all partulas. Beside it, several snail-shell necklaces lay in casual loops of pink, brown, tan, and gray. Each tiny shell had been carefully matched for colors and size, and what makes this remarkable is that, according to Bryan, even in one valley shell patterns can vary about every twenty yards. It was disturbing to see the remnants of so many tiny lives ghosting across his desk, their sticky inhabitants long extinct. Their spiraling interiors belong in a church designed by Gaudí; their eye-catching shells remain to delight and haunt us. But their empty beauty tugs at the mind.

  Once, a hundred or so species of partulas inhabited French Polynesia, where the shells of the most attractive species, brown-and-green-striped, were prized. They bore such incantatory names as Partula dolorosa, Partula mirabilis, Partula solitaria, and Partula diaphana. In the 1880s an enterprising French customs officer, who enjoyed the taste of snails, decided to start a snail farm and flog snails to islanders. The snails he chose to breed were the plump, succulent giant African snail Achatina fulica. When his snails didn’t catch on as cuisine, he tossed them into the wild, where they began raiding the local crops and gardens and hitching rides to other islands. Faced with heavy crop damage, U.S. authorities on Guam introduced a particularly voracious predator, the carnivorous Florida rosy wolfsnail, Euglandina rosea, into one orange plantation in 1977. But even snails can be picky eaters, and unfortunately the rosy wolfsnail didn’t find giant African snails tasty. Instead it dashed into the adjoining forests, where it hunted down and feasted on the partulas, which for some reason it fancied. Online one can watch ghoulish footage of the carnivores at work, plunging into the shells of small, helpless partulas and gulping them down in mouthfuls with cannibalistic gusto. Ten years later, these rosy wolfsnails commanded the whole island and had devoured fifty species of partulas. Yet another tragic tale of invasive species (and human intervention) gone awry.

  Volcanic archipelagos offer natural laboratories for studying how species evolve and reinvent themselves, and so, in the 1990s, Bryan Clarke, his wife, Ann, and their lab assistant, Chris Wade, traveled to French Polynesia to study the partulas. As it happens, I was there at almost exactly the same time; though I was not in pursuit of snails, I know the tapestry of sensations they would have worked among: The spicy sweet smell of scorched sandalwood wafting through the air. Six-man outriggers pulling swiftly past, each with a piece of tusk-shaped wood tied to one side for balance. Dogs sleeping under overturned outriggers in a budget of shade. The sky everywhere full of seabirds, and on land pairs of fairy terns perching like small white angels among the tree limbs while balancing their single egg on a branch. Men heavily tattooed, women swaying as they sang traditional songs filled with baying and keening. Small houses lining the village roads. Here and there, in the foothills, house lights sparkling from the foliage, and beyond them, raincloud-wrapped mountains steaming like volcanoes. Elaborate designs everywhere one looked—on church stones, wooden carvings, and bark cloth—curving like vines and whorling like snail shells, worlds within worlds. It was as if the native artisans had looked through microscopes into the heart of cells.

  As a tantrum of sun flashed across the cobalt-blue sea, they boarded a long red-and-white ferry, lashed to the dock by four thick ropes like a wild animal that might otherwise escape, and traveled among small islands with hillsides of bottle green and slate cliffs plunging straight into the sea. It was in this remote spell of thick foliage, light-years from the clipped lawns of England, that they desperately searched for the tiny, rare, beautifully ribboned tree snails.

  They found a handful of live partulas on the island of Moorea, but Bryan had a hunch that the ancestor of all 126 partula species might live on the lone island of ’Eua, about two and a half hours from Tonga. Thirty or forty million years older than the other islands, ’Eua isn’t volcanic but a flat chunk of Gondwanaland shelf that broke off and plunked itself next to Tonga. Would they find there the ur-snails that populated all of the Pacific islands?

  When they arrived, they discovered to their dismay that the ’Eua islanders had chopped down all of the rainforest in order to plant farms of manioc. Partula’s habitat was gone. Only one faint possibility remained. At the very bottom of ’Eua’s steep ravines, a thin line of trees nestled beside streams. Islanders didn’t risk the climb, and neither did Bryan, but Ann and Chris had come too far to turn back. Pressing on, they slogged down the gorges into the island’s deep green pockets. After three weeks of scouring the plateau, beaches, and the last shreds of rainforest on the island, all they found was one midden of empty shells in a stream at the bottom of a crevasse. Picking up the small, round shells, and turning them gently like ancient coins, they realized that they were about twenty years too late, since snail shells last only twenty years in the wild. Grief-stricken, they held the remains of an extinction in their hands.

  According to Ann, the combined loss felt too heavy to bear. Carefully packing a few of the live Partula mooreana they’d found into lunch boxes, they journeyed home to Nottingham. Most of these snails they shared with the London Zoo, which set up a captive breeding program, and Bryan and Ann began breeding the rest, aided by a technician who was a genius at caring for partulas and getting them to have babies. Unusually, even for snails, partulas don’t lay eggs, but have live babies, complete with shells on.

  “Here’s a partula with young,” Ann says, opening a book to the startling image of a snail with a perfectly formed second snail emerging from behind its head (where the reproductive organs hide). “These get born just like that.”

  “With a soft shell, surely.”

  “No, with a hard shell. They’re born as complete adult snails.”

  Curiouser and curiouser, I think. The tiny necklace-worthy striped snails that haunted the trees in the kingdom of Tonga sprang from the sides of both hermaphroditic parents fully formed with (surely this birthing might hurt?) hard calcium shells. Not to mention, during courtship they stab each other in the head with calcium “love darts” pulled from their quiver.

  Aghast at the pace of Partula’s extinction, a handful of zoos worldwide also began breeding the snails with some success, from a fenced-in partula preserve on Tahiti to the Snail Room at the London Zoo, where one can see them, small as a fingernail, slow-motion slime-skiing along the glass with their nether parts exposed. But there’s no use releasing them back into the wild while hungry packs of rosy wolfsnails still rampage.

  “When we came back with the partulas in lunch boxes we were very despondent,” Ann says wistfully, “and I think it was at that very moment Bryan and I thought of the Frozen Ark. Because we’d seen all these partulas dying out. We thought, well, we’re doing this for the snails, who else is doing it for other endangered species? We started to hunt about and we really couldn’t find anyone.”

  The Clarkes set up the Frozen Ark Project in 1996 as a response to this crisis, with a single simple objective—to save samples of frozen cells containing DNA from endangered animals before they go extinct. Not as an alternative to preserving animals in their natural environments or to keeping them in zoos, she stresses, but as crucially important extra insurance.

  Today a consortium of twenty-two of the world’s finest zoos, aquariums, museums, and research institutions have climbed aboard the Ark and are providing DNA. Only a tiny dab is needed, gathered painlessly from mouth swabs, feces, hair, feathers, or blood during routine veterinary visits. The samples are sent to Nottingham, where they’re cataloged and safely frozen, with backups stored at the home zoos. It’s convenient that DNA is thousands of times smaller than a gnat’s whisker; many individuals exist only as wispy smears on small white filter papers. A single-car garage could store a million; a briefcase could hide
enough to repopulate a continent. At the Frozen Ark, specimens hover in liquid nitrogen at -196°F, ensuring viable DNA for hundreds of thousands of years, and hundreds of years for complete cells. Nothing moves at -196°F, but in time these cells could be resurrected and recultured.

  Using Gurdon and Yamanaka’s pluripotent stem-cell work, the Clarkes discovered how the Ark’s frozen cargo could repopulate extinct or nearly extinct herds.

  “It means we can make any tissue, including eggs and sperm,” Bryan says. “Now, the importance of that is extraordinary, because you could, in principle anyway, reconstruct an entire organism, even when it’s gone. The Japanese, among others, are trying to implant a woolly mammoth embryo into an elephant which would then give birth to it. There are a lot of mammoths frozen in the permafrost. . . . Of course not for long, because it’s melting.”

  Even after ten thousand years of icy slumber, these mammoths are still a treasure trove of frozen DNA, and Bryan assures me that they’d survive freezing for even longer periods of time, and still be viable, if the right method was used.

  “I’m very keen at the moment on the idea of freeze-drying cells, you know, like your coffee.”

  I try not to picture a jar of freeze-dried woolly mammoth crystals on a shelf beside a jar of dodo crystals, rather like in a country store, but it’s no use.

  “The habitat up there in Siberia might be just fine.” Bryan settles back deeper into his chair. “The question then is: What do you do with the mammoth when you’ve got it?! That’s a sort of quandary. Is it better to have two mammoths so they can reproduce and restore the species? I think that would be fun,” he says, clearly charmed by the idea, “and I think they would find habitats they can live in.”

  It’s delightful to imagine twenty-first-century woollies, born from elephant mothers (rather surprised at their shaggy offspring?), thunder-stomping through Siberia, maybe sounding an alarm when startled by a de-extincted saber-toothed tiger.

  Yet, as we know, mothers teach their babies all kinds of things; our newborn woollies wouldn’t have a mammoth culture. Perhaps they’d imprint on their new mothers like baby ducks and adopt the elephant’s ear-flapping semaphore and yen for dust-baths. Or would they be raised like endangered baby sandhill cranes, who are fed and taught crane behaviors by white-costumed humans flying ultralights? So they’d be woolly mammoths, but not exactly. These mammoths would probably also not have the ancient ancestral suite of woolly mammoth bacterial DNA in their gut and on their skin—the tumbling parasites and symbiotic companions that help make us whole, although Ann tells me it might be possible to revive mammoth bacterial DNA, since, if the tissue is frozen, there’s a good chance the tiny piggybacked frozen smidges of bacteria that went with it would be there, too.

  So woolly mammoths and golden toads and baiji dolphins and North American camels might all haunt the Earth again. Or perhaps less controversially, the cells might be used to insert more genetic variety into dwindling populations of almost-extinct animals. Saving animals on the brink by diversifying their genome doesn’t bother most people; it’s a far cry from reincarnating dead ones.

  I’m intrigued by the idea of resurrecting Neanderthals, having learned recently that we Homo sapiens harbor between 1 and 3 percent Neanderthal DNA, and when I ask Ann her thoughts on the matter, she’s clearly fascinated by the mystery.

  “I hope I’m a very large amount of Neanderthal!” she says, eyes sparkling. “I mean, how fascinating is it? And it appears to be all in the white Anglo-Saxon gene pool! Maybe we’re the thick ones. I worry a bit about those guys. Did we polish them all off—or did they die in the cold, or something? I mean if we polished them all off—that’s terrible.”

  Her enthusiasm is refreshing, and I must say, she’s the first person I’ve met who longs to be part Neanderthal, though one of her countrymen, William Golding, wrote a poignantly picturesque novel, The Inheritors, narrated from the perspective of the last Neanderthal as his species was being exterminated by our quick, sly, talkative Homo sapiens progenitors.

  “And in the case of some wonderful extinct animal . . .”

  “Saber-toothed tiger?” she offers with clear relish.

  “Yes! But would there still be a habitat for saber-toothed tigers?”

  “Well, that’s debatable. But I personally think biodiversity is good—and if we could bring back some species that we have made extinct, I think I’d rather see them gamboling about in the fields of Kent, or in a woods, than not at all.”

  Although that’s as far as she’ll go, Ann realizes that it’s something the Ark will need to think about. They could resurrect the woolly mammoth or saber-toothed tiger or dodo or anything else that’s extinct. But they’ve decided, for the moment, to stop when they collect the genetic material. With the DNA of two million to seven million species still to back up, their project is far from finished.

  “But it won’t stop there,” she says with a sibylline smile.

  As we well know (think of the cannibal snails on Moorea), introducing new species can have unexpected consequences. And, yes, de-extinction is a divisive topic, even among the diverse members of the Frozen Ark’s own consortium. A chief concern from naysayers is that it would divert attention from the serious work of conservation—protecting animals and ecosystems from going extinct in the first place. Critics also worry about the DNA of extinct species weaving through wild populations as ancient newcomers, a different kind of invasive species, one from the past. Both concerns are undoubtedly valid. I’m also troubled by how de-extinction plays into an increasingly mercantile view of life in which most anything is disposable and replaceable by a newer synthetic model. On the other hand, like Ann, I’d really love to see a formerly extinct zebralike creature “gamboling in the fields of Kent.”

  Collecting DNA is one thing; agreeing on what to do with it is another. From the Frozen Ark’s point of view, there is enough work saving the DNA. Future generations can decide what to do with it in light of the new technologies that emerge. What began as an effort to bank the DNA of only the most endangered animals has now evolved into an urgent banking of whole ecosystems. The Ark goes into an area and collects everything that crawls, flies, scampers, or slithers. In a tropical rainforest with its thick canopy, groups of people spread sheets underneath a tree, and they shake it. As I picture raining insects, frogs, snails, and moths, I feel sure Ann finds the shaking and collecting great fun. I know I would. We haven’t named more than about 65 percent of the biomass of all the species on Earth. So, yes, shake it down, and freeze it, and take it to the Natural History Museum, and label it—so we can tell whether it’s an ant or bee or moth—and let the taxonomists name it officially later.

  Nottingham stores the DNA of the courtship-crooning Mississippi alligator, giant squid with dinner-plate-sized eye, secretive snow leopard, blue-throated macaw from the Bolivian rainforest, iconic African lion, and square-lipped northern white rhino, among many others. My mind’s eye automatically pictures each species in turn. Only about 20 percent of the species are on the endangered species list, and some are not endangered at all. Ideally, the Frozen Ark would store DNA from every species on Earth, but that’s not practical. The mammals would be easy, but the bugs would take a long while, especially the beetles, since there are more beetles than anything else on planet Earth (one of my favorites being the dung beetles who navigate by the stars like ancient mariners).

  As I set down my cell phone, Ann notices my screen saver of an insanely cute baby wombat, a face that could melt a thousand hearts, and her eyes widen in appreciation. She’s just returned from a meeting in Sydney, so I ask her how the cancer-plagued Tasmanian devils are doing.

  “They can cure the cancer in captivity,” Ann replies, her face showing her concern, “but it’s the ones in the wild that are the worry.” With a grim nod, she continues, “And the koalas have got chlamydia. And I heard some of the wombats are getting sick.”

  Just over a hundred of the northern hairy-nosed wombats, the wo
rld’s cuddliest marsupial, survive in a tiny plot of Queensland. Though once numerous all across Australia, they feed on grasses, and when humans arrived with agriculture and herds of cattle (essentially four-legged mowers), the wombats simply couldn’t compete. Drought and invasive species have been polishing off the wombat’s supply of native spear, tussock, and poa grasses. It’s hard to picture Australia minus most of its famous creatures. Conservationists are trying to treat them in the wild, but Ann doesn’t think that Australia’s terribly worried about the extinction of its animals.

  “They’ve got this beautiful country and everything looks perfect, and there’s not huge numbers of people crashing about,” she says.

  “So they think it’s forever.”

  “They think it’s forever,” Ann repeats with incredulous fervor. “But I think Americans are more interested in conservation. Don’t you think so?”

  In my experience, I tell her, Americans are deeply concerned about conservation, but we have clashing, fiercely defended opinions about how to do it. Some believe it’s essential to preserve our majestic national parks; some, that the parks are a lost crusade and that safeguarding animals in big preserves just hasn’t worked. Some believe in rewilding’s networks of “cores, corridors, and carnivores” to reconnect and rebalance unstable ecosystems; or Pleistocene rewilding—in North America, unloosing elephants, lions, bison, and cheetahs (the closest living relatives of the ancient native megafauna) to roam the Great Plains. Others argue that all of the above are last-epoch thinking, and, as an increasingly metropolitan species, we should weave more of the wild into the cities where we live. Ann feels certain that we need multifaceted solutions.